The origin of asteroid Kamo’oalewa, discovered in 2016, has puzzled scientists for years, but recent research suggests that it could be a chunk of the Moon. A team of astronomers led by Yifei Jiao of Tsinghua University in China believes they’ve found the source crater from which the asteroid might have been dislodged: the Giordano Bruno crater, located on the far side of the Moon.
Using numerical simulations, the team examined the properties of the asteroid, focusing on its orbital dynamics and physical characteristics. They concluded that the impact responsible for creating the Giordano Bruno crater could have launched fragments into space, eventually resulting in Kamo’oalewa orbiting near Earth.
In their paper, the researchers write, “We have explored the processes for impact-induced lunar fragments migrating into Earth co-orbital space and presented support for Kamo’oalewa’s possible origin from the formation of the Giordano Bruno crater a few million years ago.” If this link is proven, it could indicate the existence of more small asteroids made of lunar material in near-Earth space.
Earth has just one large natural satellite, but there are also smaller ‘minimoons’ orbiting nearby, which are often overlooked due to their elusiveness. Kamo’oalewa, for example, has been sharing Earth’s orbital space for centuries, but its varying distance from Earth made it tricky to detect until it was eventually discovered.
The mystery deepened due to Kamo’oalewa’s unique reflective properties and color, which are similar to the lunar surface but unlike other near-Earth asteroids. This led scientists to speculate that the asteroid could be a piece of the Moon.
Jiao’s team then took the research further, looking at the asteroid’s physical and orbital properties to determine the impact event that could have caused its creation. The rapid rotation rate of Kamo’oalewa indicates it’s a solid lump rather than a loose collection of debris, suggesting it was excavated from the Moon as a single chunk.
The researchers deduced that the impact needed to create such an asteroid would have left a crater larger than 10 to 20 kilometers in diameter. Given the lifespan of near-Earth asteroids, Kamo’oalewa likely formed between 10 and 100 million years ago. The Giordano Bruno crater, at 22 kilometers across and less than 10 million years old, matches these criteria.
“The largest, youngest craters are more probable sources, as they produce more escaping fragments that still remain in space or the Earth co-orbital region,” the researchers explain. Giordano Bruno fits the bill, with up to 400 Kamo’oalewa-sized fragments possibly ejected during the impact.
Simulations suggest that most fragments from such an event would be flung out of Earth’s co-orbital space within 10 million years, but a rare few could remain and settle into orbits like Kamo’oalewa’s.
The study’s findings, while not definitive, open new possibilities for understanding the origins of asteroids. The Chinese National Space Administration plans to launch Tianwen-2, an asteroid-sampling mission, next year to explore Kamo’oalewa and bring back samples for Earth-based analysis. This could help confirm whether Kamo’oalewa is indeed a piece of the Moon and shed light on the other fragments that may still be out there.
The research has been published in Nature, and it’s expected to inspire further studies on asteroids and their potential lunar origins. As technology and exploration efforts advance, astronomers may soon uncover more mysteries of our solar system’s history.
